1. Technical Field
The present invention relates to a pattern forming method, a resist pattern formed by the method, a method for manufacturing an electronic device using the same, and an electronic device. More specifically, the present invention relates to an ultra-micro lithography process which may be applied to a process of manufacturing ultra LSI and high capacity microchips, a process of preparing a mold for nanoimprinting, a process of producing a high-density information recording medium, and the like, a pattern forming method which is suitably used in other photo fabrication processes, a resist pattern formed by the method, a method for manufacturing an electronic device using the same, and an electronic device.
2. Background Art
Since the advent of a resist for KrF excimer laser (248 nm), an image forming method called chemical amplification has been used as an image forming method of the resist in order to compensate for sensitivity reduction caused by light absorption. For example, the image forming method by a positive-type chemical amplification is an image forming method of decomposing an acid generator in the exposed portion by exposure to generate an acid, converting an alkali insoluble group into an alkali soluble group by using the generated acid as a reaction catalyst in the baking after exposure (PEB: Post Exposure Bake), and removing the exposed portion by alkali development. A positive-type image forming method using such a chemical amplification mechanism has currently become a mainstream process.
However, in the positive-type image forming method as described above, in a case of forming the isolated space or fine hole patterns, the shape of the patterns easily deteriorates.
From the viewpoint of solving these problems, a method is known, in which after a positive-type pattern is first formed by exposure and development, the positive-type pattern is made to be alkali-soluble, and then a negative-type resist pattern is formed by applying a reversal film thereon, and dissolving the positive-type pattern by alkali etching to reverse the film pattern into a negative-type pattern (see Japanese Patent No. 4826846 and Japanese Patent Application Laid-Open No. 2009-301007), but there is a problem in that the process is complicated, such as requirement to convert the positive-type pattern into being alkali soluble before the reversal film is applied.
Meanwhile, in recent years, with high integration of integrated circuits, ultrafine pattern formation of a sub-micron or quarter-micron region has been required. Accordingly, the exposure wavelength also shows a tendency to be a shorter wavelength, and thus development of lithography using electron beams, or X-rays, or EUV light has also proceeded.
The lithography using electron beams, or X-rays, or EUV light is ranked as a next-generation or next-next-generation pattern formation technique, thereby leading to development of an ultrafine pattern formation method, and line thinning has been further pursued.
From the viewpoint of such line thinning, a pattern forming method using a developer (organic-based developer) including an organic solvent has also been developed (see, for example, Japanese Patent Application Laid-Open No. 2010-217884). According to the method, it is considered that a high-precision fine pattern may be stably formed.
However, the more line thinning is pursued as described above, pattern collapse easily occurs, so that thinning of the resist film is required from the viewpoint of preventing such pattern collapse.
However, the thinner the resist film becomes as a result of pursuing the line thinning, etching resistance of the resist film may disappear, so that a dilemma in which the film fails to function as a resist film may occur.
As described above, the line thinning and the etching resistance as a function of the resist film are in a trade-off relationship, and thus it is important how to simultaneously satisfy both the line thinning and the etching resistance.
Further, in the positive-type image forming method, it is said that an isolated line or a dot pattern may be satisfactorily formed, but it is currently difficult to form a fine isolated line pattern having a line width of approximately 25 to 30 nm, or form a dot pattern having a fine dot diameter (for example, approximately 25 to 30 nm).
An object of the present invention is to provide a pattern forming method, which may form a fine pattern, such as a fine isolated line pattern or a fine dot pattern, which is difficult to form in a positive-type pattern forming method in the related art, may solve a dilemma of line thinning and the development of etching resistance by using a resist film for reversing a specific pattern, and thus may form a pattern which has a good roughness performance such as line width roughness (LWR) and may sufficiently withstand etching even though the pattern is fine, a resist pattern formed by the method, a method for manufacturing an electronic device using the same, and an electronic device.